JP6098159B2 - Method for producing cyclic polyarylene sulfide - Google Patents

Description

  The present invention relates to a method for producing a cyclic polyarylene sulfide. More specifically, the present invention relates to a method for efficiently producing a cyclic oligoarylene sulfide in a short time by an economical and simple method.

  Aromatic cyclic compounds can be applied to highly functional materials and functional materials based on the properties resulting from their cyclic properties, such as properties as compounds with inclusion ability, and high molecular weight linear forms by ring-opening polymerization In recent years, it has attracted attention due to its specificity derived from its structure, such as its use as an effective monomer for polymer synthesis. Cyclic polyarylene sulfide (hereinafter, polyarylene sulfide may be abbreviated as PAS) also belongs to the category of aromatic cyclic compounds and is a notable compound as described above.

  As a method for producing a cyclic polyarylene sulfide, for example, a method of oxidative polymerization of a diaryl disulfide compound under ultra-dilution conditions has been proposed (see, for example, Patent Document 1). In this method, it is presumed that cyclic polyarylene sulfide is produced with high selectivity, and that only a small amount of linear polyarylene sulfide is produced, and it is considered that cyclic polyarylene sulfide is obtained in high yield. However, in this method, it is essential to carry out the reaction under ultra-dilution conditions, and the amount of cyclic polyarylene sulfide obtained per unit volume of the reaction vessel is very small, and cyclic polyarylene sulfide can be obtained efficiently. From this point of view, it was a method with many problems. Moreover, this method is a method using oxidative polymerization, and since this method requires mild conditions around room temperature, the reaction requires a long time of several tens of hours and is inferior in productivity. Furthermore, the polyarylene sulfide by-produced by this method has a low molecular weight including a disulfide bond derived from the starting diaryl disulfide and has a molecular weight close to that of the target cyclic polyarylene sulfide. It was difficult to separate the by-product polyarylene sulfide, and it was extremely difficult to efficiently obtain a high-purity cyclic polyarylene sulfide. In addition, this method requires an equivalent amount of an expensive oxidizing agent such as dichlorodicyanobenzoquinone as the starting diaryl disulfide for the progress of the oxidative polymerization, and it has not been possible to obtain a cyclic polyarylene sulfide at a low cost. A method of utilizing oxygen as an oxidant in the presence of a metal catalyst in oxidative polymerization has also been proposed. In this method, the oxidant is inexpensive, but the reaction is difficult to control and a large amount of by-product oligomers are produced. On the other hand, there are many problems such as the necessity of an extremely long time for the reaction, and in any case, it was not possible to efficiently obtain a cyclic polyarylene sulfide having a high purity at low cost.

  As another method for producing cyclic polyarylene sulfide, a method in which a copper salt of 4-bromothiophenol is heated under ultra-diluted conditions in quinoline is disclosed. In this method as well, the ultra-dilution conditions are indispensable as in the case of Patent Document 1, and a long time is required for the reaction, and the method is extremely low in productivity. Furthermore, in this method, it is difficult to separate the by-produced copper bromide from the product cyclic polyarylene sulfide, and the resulting cyclic polyarylene sulfide has low purity (see, for example, Patent Document 2). .)

  As a method for producing cyclic polyarylene sulfide from a general-purpose raw material, p-dichlorobenzene as a dihalogenated aromatic compound and sodium sulfide as an alkali metal sulfide are reacted in N-methylpyrrolidone which is an organic polar solvent, Next, a method for recovering polyphenylene sulfide obtained by removing the solvent under heat and reduced pressure and then washing with water from the saturated solution portion of the extract obtained by extraction with methylene chloride is disclosed (for example, patents). Reference 3). This method has a problem that most of the product is high molecular weight polyphenylene sulfide, and only a very small amount (less than 1% yield) of cyclic polyarylene sulfide is obtained.

  As a method of obtaining an arylene sulfide-based polymer using linear polyarylene sulfide as a raw material, an alkali thiolate group is present at at least one terminal obtained by depolymerization by causing an alkali metal sulfide to act on the polyarylene sulfide. A method of polymerizing a prepolymer and a dihalogenated aromatic compound is disclosed (for example, see Patent Document 4). This method relates to the modification of polyarylene sulfide. In this method, after obtaining a prepolymer having an alkali thiolate group at at least one terminal by first reacting polyarylene sulfide and alkali metal sulfide, It is essential to undergo a two-step reaction of polymerizing this prepolymer and dihalogenated aromatic compound. Compared to the method of reacting linear polyarylene sulfide, sulfidizing agent and dihalogenated aromatic compound at once, the reaction Therefore, there are many problems to be solved, such as the need for strict control and the complicated operation.

  Further, a reaction mixture comprising a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent is reacted, and a cyclic polyarylene sulfide mixture containing the obtained cyclic polyarylene sulfide and linear polyarylene sulfide is used. It is disclosed that the arylene sulfide is separated and the remaining linear polyarylene sulfide is added to the reaction mixture as a raw material for the reaction and reused. (For example, refer to Patent Document 5.) In the above reaction, precise adjustment of the composition of the reaction mixture is required. However, there is no disclosure regarding measuring the amount of linear polyarylene sulfide to be recycled and adjusting the composition accordingly. Therefore, when the linear polyarylene sulfide is reused when the concentration of the linear polyarylene sulfide varies and the composition ratio of the reaction mixture deviates from the desired range, the yield of the obtained cyclic polyarylene sulfide is reduced. There is a problem that decreases.

Japanese Patent No. 3200027 US Pat. No. 5,869,599 JP 05-163349 A Japanese Patent Laid-Open No. 04-7334 Japanese Patent Laid-Open No. 21-227952

  It is an object of the present invention to provide a method for producing industrially useful cyclic polyarylene sulfide in a high yield.

  The inventors of the present invention have reached the present invention as a result of intensive studies and studies in order to solve such problems.

That is, the present invention
(1) A method for producing a cyclic polyarylene sulfide by heating and reacting a reaction mixture containing at least a linear polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent, From a polyarylene sulfide mixture containing a cyclic polyarylene sulfide and a linear polyarylene sulfide obtained by heating and reacting a reaction mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent, In the method of reusing a mixed slurry containing a linear polyarylene sulfide and an organic polar solvent obtained by separating a polyarylene sulfide of the formula, the mixed slurry is measured by measuring the temperature, density and flow rate of the mixed slurry. Linear polyarylene contained in Constantly measuring the concentration of Rufido, and adjust the flow rate of the mixed slurry according to the concentration of the linear polyarylene sulfide in the mixed slurry, the mixed slurry, sulfidizing agent, dihalogenated aromatic compound, an organic polar solvent A method for producing a cyclic polyylene sulfide, which is recycled to a reaction mixture containing
(2) The method for producing the cyclic polyarylene sulfide according to (1), wherein the temperature, density, and flow rate of the mixed slurry are measured by a Coriolis mass flow meter,
It is.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to make the quantity of the arylene unit per fixed amount of sulfur components in the reaction mixture in the reaction composition appropriate, and a method for producing cyclic polyarylene sulfide in a high yield. Can be provided.

FIG. 1 is a diagram showing process steps of a method for producing a cyclic polyarylene sulfide according to the present invention.

(1) Sulfiding agent The sulfidizing agent used in the present invention may be any one that can introduce a sulfide bond into a dihalogenated aromatic compound, or that can act on an arylene sulfide bond to produce an arylene thiolate. Examples include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide.

  Specific examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide and a mixture of two or more thereof, among which lithium sulfide and / or sodium sulfide are preferable. Sodium sulfide is more preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides. The aqueous mixture refers to an aqueous solution, a mixture of an aqueous solution and a solid component, or a mixture of water and a solid component. Since generally available inexpensive alkali metal sulfides are hydrates or aqueous mixtures, it is preferred to use such forms of alkali metal sulfides.

  Specific examples of the alkali metal hydrosulfide include, for example, lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures of two or more thereof. Lithium hydrosulfide and / or sodium hydrosulfide are preferable, and sodium hydrosulfide is more preferably used.

  Moreover, the alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. Alternatively, an alkali metal sulfide prepared by previously contacting an alkali metal hydrosulfide and an alkali metal hydroxide can be used. These alkali metal hydrosulfides and alkali metal hydroxides can be used as hydrates or aqueous mixtures, or in the form of anhydrides. From the viewpoint of availability and cost of hydrates or aqueous mixtures. preferable.

  Furthermore, an alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide and hydrogen sulfide can also be used. Further, alkali metal sulfides prepared by previously contacting alkali metal hydroxides such as lithium hydroxide and sodium hydroxide with hydrogen sulfide can also be used. Hydrogen sulfide can be used in any form of gas, liquid, and aqueous solution.

  In the present invention, the amount of the sulfidizing agent is determined from the actual charge amount when a partial loss of the sulfidizing agent occurs before the start of the reaction between the linear polyarylene sulfide and the dihalogenated aromatic compound due to dehydration operation or the like. It shall mean the remaining amount after deducting the loss.

  An alkali metal hydroxide and / or an alkaline earth metal hydroxide can be used in combination with the sulfidizing agent. Specific examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture of two or more thereof. Specific examples of the metal hydroxide include, for example, calcium hydroxide, strontium hydroxide, barium hydroxide, and sodium hydroxide is preferably used.

  When an alkali metal hydrosulfide is used as the sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time, but the amount used is 0.95 to 1. A range of 50 moles, preferably 1.00 to 1.25 moles, more preferably 1.005 to 1.200 moles can be exemplified. When hydrogen sulfide is used as the sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time. The amount of the alkali metal hydroxide used in this case is 2.0 to 3.0 with respect to 1 mole of hydrogen sulfide. The range of mol, Preferably it is 2.01-2.50 mol, More preferably, it is 2.04-2.40 mol.

(2) Dihalogenated aromatic compound As the dihalogenated aromatic compound used in the production of the cyclic PAS of the present invention, p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene, o- Dihalogenated benzene such as dibromobenzene, m-dibromobenzene, 1-bromo-4-chlorobenzene, 1-bromo-3-chlorobenzene, and 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-di Dihalogenated aromatic compounds containing substituents other than halogen such as chlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene, 1,3-dimethyl-2,5-dichlorobenzene and 3,5-dichlorobenzoic acid And so on. Especially, the dihalogenated aromatic compound which has p-dihalogenated benzene represented by p-dichlorobenzene as a main component is preferable. Particularly preferably, it contains 80 to 100 mol%, more preferably 90 to 100 mol% of p-dichlorobenzene. It is also possible to use two or more different dihalogenated aromatic compounds in combination in order to produce a cyclic PAS copolymer.

  The amount of the dihalogenated aromatic compound used is preferably in the range of 0.9 to 2.0 mol, more preferably in the range of 0.95 to 1.5 mol, per mol of the sulfur component of the sulfiding agent. The range of .98 to 1.2 mol is more preferable.

(3) Linear polyarylene sulfide The linear PAS in the present invention is a linear PAS having a repeating unit of the formula, — (Ar—S) —, preferably containing 80 mol% or more of the repeating unit. A homopolymer or a linear copolymer. Ar includes units represented by the following formulas (A) to (L), among which the formula (A) is particularly preferable.

(In the formula, R1 and R2 are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group, and R1 and R2 are the same or different. May be good.)
As long as this repeating unit is a main structural unit, it can contain a small amount of branching units or crosslinking units represented by the following formulas (M) to (P). The amount of copolymerization of these branched units or cross-linked units is preferably in the range of 0 to 1 mol% with respect to 1 mol of-(Ar-S)-units.

  Further, the linear PAS in the present invention may be any of a random copolymer, a block copolymer and a mixture thereof containing the above repeating unit.

  Typical examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers thereof, block copolymers, and mixtures thereof. Particularly preferred PASs include p-phenylene sulfide units as the main structural unit of the polymer.

In addition to polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) containing 80 mol% or more, particularly 90 mol% or more, polyphenylene sulfide sulfone and polyphenylene sulfide ketone.

  The melt viscosity of various linear PASs in the present invention is not particularly limited, but the melt viscosity of general linear PAS can be exemplified by a range of 0.1 to 1000 Pa · s (300 ° C., shear rate 1000 / sec). The range of 0.1 to 500 Pa · s is a preferable range from the viewpoint of easy availability. Further, the molecular weight of the linear PAS is not particularly limited, and general PAS can be used. Examples of the weight average molecular weight of such a PAS include 1,000 to 1,000,000, 500-500,000 are preferable and 5,000-100,000 are more preferable. In general, the lower the weight average molecular weight, the higher the solubility in an organic polar solvent. Therefore, there is an advantage that the time required for the reaction can be shortened, but within the above-mentioned range, it can be used without any substantial problem.

  In general, the production of a cyclic compound includes the present invention, and is a competitive reaction between the production of a cyclic compound and the production of a linear compound. In addition to PAS, linear PAS is generated as a by-product. In the present invention, such a by-product linear PAS can be used as a raw material without any problem. For example, 1.25 liters of a sulfidizing agent and a dihalogenated aromatic compound are used per 1 mol of the sulfur component of the sulfidizing agent. It was obtained by separating cyclic polyarylene sulfide from a polyarylene sulfide mixture containing cyclic polyarylene sulfide and linear polyarylene sulfide obtained by heating and reacting using the above organic polar solvent. The method using linear polyarylene sulfide is a particularly preferable method. Further, a linear polyarylene sulfide produced by the practice of the present invention, that is, a reaction mixture composed of at least a linear polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent is converted into a sulfur component in the reaction mixture. From a polyarylene sulfide mixture containing a cyclic polyarylene sulfide and a linear polyarylene sulfide obtained by heating and reacting using 1.25 liters or more of an organic polar solvent per mole, a cyclic polyarylene sulfide is obtained. The use of linear polyarylene sulfide obtained by separation is a particularly preferable method. Conventionally, a cyclic compound, a linear compound by-produced in the production of cyclic PAS, and linear PAS have been discarded as having no utility value. Therefore, in the production of the cyclic compound, there are problems that the amount of waste caused by the by-product linear compound is large and the yield relative to the raw material monomer is low. In the present invention, this byproduct linear PAS can be used as a raw material, which is significant in terms of enabling a significant reduction in the amount of waste and a dramatic improvement in the yield relative to the raw material monomer. It is.

  The amount of linear PAS used is not limited as long as linear PAS is contained in the reaction mixture at the start of the reaction, that is, when the conversion rate of the dihalogenated aromatic compound charged in the reaction system is zero. Is preferably in the range of 0.1 to 20 repeating unit moles per mole of sulfur component of the sulfidizing agent, based on the repeating unit of the formula — (Ar—S) — which is the main structural unit of A range of 15 repeating unit moles is more preferred, and a range of 1 to 10 repeating unit moles is even more preferred. When the amount of linear PAS used is within a preferred range, cyclic PAS tends to be obtained in a high yield, and the reaction tends to proceed in a shorter time.

(4) Organic Polar Solvent In the production of the cyclic PAS of the present invention, an organic polar solvent is used as a reaction solvent. Among them, an organic amide solvent is preferably used. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone, caprolactam such as N-methyl-ε-caprolactam and ε-caprolactam. , Aprotic organic polar solvents represented by 1,3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric triamide, and the like, It is preferably used because of its high reaction stability. Among these, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used.

  In the present invention, the amount of the organic polar solvent used as the reaction solvent in the production of cyclic PAS is 1.25 liters or more, preferably 1.5 liters or more, more preferably, with respect to 1 mole of the sulfur component contained in the reaction mixture. 2 liters or more. In addition, the sulfur component which a reaction mixture contains here is the sum total of the sulfur component contained in the sulfur component contained in the linear polyarylene sulfide used for a raw material, and the sulfidizing agent used for a raw material. Here, the “number of moles” of the sulfur component contained in the linear polyarylene sulfide is the “number of repeating units” of the polymer containing one sulfur atom. For example, one molecule of linear polyphenylene sulfide having a degree of polymerization of 100 is calculated as 100 mol, not 1 mol. As long as the essence of the present invention is not impaired, a compound containing a sulfur component in addition to the linear polyarylene sulfide and the sulfidizing agent can be additionally present in the reaction mixture. Thus, sulfur components derived from sulfur-containing compounds that do not substantially act may not be taken into account. Further, the upper limit of the amount of the organic polar solvent is not particularly limited, but it is preferably 50 liters or less with respect to 1 mol of the sulfur component contained in the reaction mixture from the viewpoint of more efficiently producing cyclic PAS. More preferably, it is more preferably 15 liters or less. Here, the amount of solvent used is based on the volume of the solvent under normal temperature and pressure. When the amount of the organic polar solvent used is increased, the selectivity of cyclic PAS production is improved. However, when the amount is too large, the production amount of cyclic PAS per unit volume of the reaction vessel tends to decrease. There is a tendency that the time required is longer. It is preferable to make it the usage-amount range of an organic polar solvent mentioned above from a viewpoint of making the production | generation selectivity of cyclic PAS and productivity compatible. Here, the amount of the organic polar solvent used in the reaction mixture is an amount obtained by subtracting the organic polar solvent removed from the reaction system from the organic polar solvent introduced into the reaction system.

(5) Cyclic polyarylene sulfide The cyclic polyarylene sulfide in the present invention is a cyclic compound having a repeating unit of formula:-(Ar-S)-as a main constituent unit, and preferably 80 mol of the repeating unit. % Or more of the compound represented by the following general formula (Q).

  Here, examples of Ar can include units represented by the formulas (A) to (L), among which the formulas (A) to (C) are preferable, and the formulas (A) and (B) are more preferable. Formula (A) is particularly preferable.

  In addition, in cyclic polyarylene sulfide, repeating units, such as said Formula (A)-Formula (L), may be included at random, may be included in a block, and any of those mixtures may be sufficient. Typical examples of these include cyclic polyphenylene sulfide, cyclic polyphenylene sulfide sulfone, cyclic polyphenylene sulfide ketone, cyclic random copolymers containing these, cyclic block copolymers, and mixtures thereof. . Particularly preferred cyclic polyarylene sulfides include p-phenylene sulfide units as the main structural unit.

Is a cyclic polyphenylene sulfide containing 80 mol% or more, particularly 90 mol% or more (hereinafter sometimes abbreviated as cyclic PPS).

  Although there is no restriction | limiting in particular in the repeating number m in the said (Q) formula of cyclic polyarylene sulfide, 2-50 are preferable, 2-25 are more preferable, and 3-20 can be illustrated as a still more preferable range. As will be described later, when the polyarylene sulfide prepolymer containing cyclic PAS is converted into a high degree of polymerization, it is preferably heated at a temperature higher than the melting point of the cyclic polyarylene sulfide. Since the melting temperature of the cyclic polyarylene sulfide tends to be higher when the value of the polyarylene sulfide is increased, the conversion of the polyarylene sulfide prepolymer to a high degree of polymerization can be performed at a lower temperature. The above range is advantageous.

  The cyclic polyarylene sulfide may be either a single compound having a single repeating number or a mixture of cyclic polyarylene sulfides having different repeating numbers, but may be a mixture of cyclic polyarylene sulfides having different repeating numbers. The melt solution temperature tends to be lower than that of a single compound having a single number of repetitions, and the use of a mixture of cyclic polyarylene sulfides having different numbers of repetitions is used in the conversion to the above-mentioned high degree of polymerization. This is preferable because the temperature can be lowered.

(6) Method for Producing Cyclic Polyarylene Sulfide In the present invention, a reaction mixture comprising at least a linear polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent is heated and reacted to form a cyclic product. Polyarylene sulfide is produced.
FIG. 1 shows process steps of a method for producing a cyclic polyarylene sulfide according to the present invention. This process step includes a raw material adjustment step, a reaction step, a cyclic polyarylene sulfide recovery step, a linear polyarylene sulfide reuse step, and a linear polyarylene sulfide reuse step.

(Raw material adjustment process)
In the method for producing cyclic PAS of the present invention, first, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent are charged into a reactor, and the reaction is carried out as a reaction mixture containing these as essential components.

  A cyclic polyarylene sulfide and a linear polyarylene sulfide are produced by the reaction, and these are separated by a separation step described later, and the linear polyarylene sulfide is reused as a raw material. That is, linear polyarylene sulfide is not contained in the raw material immediately after the start of the reaction, but after the polyarylene sulfide produced as a by-product begins to be reused once, the raw material contains linear polyarylene sulfide. .

  The total amount of the arylene units in the reaction mixture, the arylene units derived from the newly added dihalogenated aromatic compound, and the arylene units derived from the linear polyarylene sulfide added by recycling is the sulfur component 1 in the reaction mixture. It is important to adjust the raw materials so that the number of arylene units per mole is in the range of 1.05 mol to 1.50 mol in order to improve the purity and yield of the cyclic polyarylene sulfide. Here, the lower limit of the total amount of the arylene units after addition of the dihalogenated aromatic compound is 1.05 mol per mol of the sulfur component in the reaction mixture, and preferably 1.06 mol. The upper limit is 1.50 mol, preferably 1.30 mol, more preferably 1.20 mol, even more preferably 1.15 mol, and still more preferably 1.12 mol. The arylene unit in the reaction mixture refers to the total of the arylene unit derived from the dihalogenated aromatic compound contained in the reaction mixture and the arylene unit derived from the arylene sulfide compound present in the reaction mixture.

  The order in which these components are charged into the reactor is not particularly limited, but a method of first charging all or a part of the organic polar solvent to be used and then charging the other components is preferable for homogenizing the reaction mixture. In addition to the essential components, a third component that does not significantly inhibit the reaction and a third component that has an effect of accelerating the reaction can be added to the reaction mixture. Although there is no restriction | limiting in particular in the method of performing reaction, Performing on stirring conditions is preferable for homogenization of a reaction system. In addition, there is no restriction | limiting in particular in the temperature at the time of charging the said raw material here, For example, you may react after charging a raw material near room temperature, or you may supply a raw material to the reactor temperature-controlled beforehand to the temperature preferable for reaction mentioned above. It is also possible to carry out the reaction by charging. It is also possible to continuously carry out the reaction by sequentially charging the raw material into the reaction system in which the reaction is performed.

It is also possible to use a sulfidizing agent, a dihalogenated aromatic compound, linear PAS, and an organic polar solvent containing water. In general, in the reaction using a sulfidizing agent and a dihalogenated aromatic compound, the reaction rate tends to decrease as the amount of water in the reaction mixture increases. Since the reaction proceeds very quickly, it is possible to perform a sufficient reaction without strictly controlling the amount of water in the reaction mixture. Therefore, the amount of water in the reaction mixture of the present invention is not particularly limited, but at the time when the reaction starts, that is, when the conversion rate of the dihalogenated aromatic compound (hereinafter sometimes abbreviated as DHA) charged to the reaction system is zero. The water content can be exemplified as a preferable range of 0.2 mol or more and 20 mol or less per mol of sulfur component in the reaction mixture, preferably 0.5 mol or more and 10 mol or less, 0.6 mol or more and 8 mol or less. Is more preferable. When the sulfidizing agent, organic polar solvent, dihalogenated aromatic compound, linear PAS and other components that form the reaction mixture contain water, the reaction starts when the amount of water in the reaction mixture exceeds the above range. It is possible to reduce the amount of water in the reaction system before or during the reaction, and to keep the amount of water within the above range, which tends to yield a cyclic PAS efficiently in a short time. . In addition, when the water content of the reaction mixture is less than the above preferable range, it is also a preferable method to add water so that the above water content is obtained. The DHA conversion rate is a value calculated by the following equation. The remaining amount of DHA can be usually determined by gas chromatography.
When dihalogenated aromatic compound is added excessively in a molar ratio with respect to the sulfidizing agent, conversion rate (%) = [[DHA charge (mol) −DHA remaining amount (mol)] / [DHA charge (mol) − DHA excess (mole)]] × 100%
In other cases, conversion (%) = [[DHA charge (mol) −DHA remaining amount (mol)] / [DHA charge (mol)]] × 100%

  Further, in the production of cyclic PAS, at an optional stage where the reaction is continued for a desired time and the charged raw materials are reduced, any one or more of linear PAS, sulfidizing agent, dihalogenated aromatic compound and organic polar solvent is used. It is also possible to continue the reaction by adding. It is important to consider the amount of the sulfur component in the reaction mixture before the addition, and the amount of the organic polar solvent added relative to 1 mol of the sulfur component in the reaction mixture after the addition of the raw material. It is strongly desired that the addition be performed within a range of 1.25 liters or more.

  As described above, the addition of linear PAS, sulfidizing agent and dihalogenated aromatic compound allows an optional stage in which the charged raw materials are reduced, but the conversion rate of DHA is 50% or more. The above stage is preferable, and a stage of 70% or more is more preferable. By adding at such a stage, it becomes possible to obtain cyclic PAS more efficiently.

  In addition, when the amount of water in the reaction mixture changes due to the addition of the raw material, it is also possible to perform an additional operation so as to achieve the above-described preferable amount of water. It is also desirable to later remove any amount of water from the reaction mixture. In the removal of water, when components other than water are removed from the reaction mixture, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent can be further added as necessary. The operation of returning the components to the reaction mixture may be performed again.

(Reaction process)
In the production of the cyclic PAS of the present invention, it is preferable to heat the reaction mixture composed of the above components beyond the reflux temperature of the reaction mixture under normal pressure. Here, the normal pressure is a pressure in the vicinity of the standard state of the atmosphere, and is an atmospheric pressure condition in which the temperature is approximately 25 ° C. and the absolute pressure is approximately 101 kPa. The reflux temperature is a temperature at which the liquid component of the reaction mixture repeats boiling and condensation. Examples of the method for bringing the reaction mixture into a heated state exceeding the reflux temperature under normal pressure include a method of reacting the reaction mixture under a pressure exceeding normal pressure and a method of heating the reaction mixture in a sealed container.

  A more preferable reaction temperature in the production of the cyclic PAS of the present invention is a temperature at which the linear PAS used as a raw material melts in the reaction mixture. The raw material linear PAS is generally in a solid state near room temperature. In the solid state, the formation reaction of cyclic PAS is difficult to proceed, but the reaction is performed at a temperature at which the linear PAS melts and dissolves. There is a tendency that the reaction system becomes uniform and the reaction rate dramatically improves, and the time required for the reaction can be shortened. This temperature cannot be determined uniquely because it varies depending on the type and amount of components in the reaction mixture, the structure of the linear PAS used as a raw material, the molecular weight, etc., but is usually 120 to 350 ° C., preferably 200 to 320. C., more preferably 230 to 300.degree. C., and still more preferably 240 to 280.degree. In this preferred temperature range, a higher reaction rate can be obtained, the reaction tends not only to be uniform and easy to proceed, but also the generated cyclic PAS tends to be less likely to be decomposed. It tends to be. The reaction may be a one-step reaction performed at a constant temperature, a multi-step reaction in which the temperature is raised stepwise, or a reaction in which the temperature is continuously changed.

  The reaction time depends on the structure and molecular weight of the linear PAS of the raw material used, the sulfidizing agent, dihalogenated aromatic compound, the type of organic polar solvent, the amount of these raw materials, or the reaction temperature, so it is generally specified. Although not possible, 0.1 hour or more is preferable, and 0.5 hour or more is more preferable. By setting it as this preferable time or more, since unreacted raw material components can be reduced sufficiently, cyclic PAS can be produced with good yield, and the produced cyclic PAS tends to be easily recovered. On the other hand, although there is no particular upper limit to the reaction time, the method of the present invention has a characteristic that an extremely high reaction rate can be easily obtained, so that the reaction proceeds sufficiently even within 10 hours, preferably within 6 hours, more preferably 3 Can be used within hours.

  In the production of the cyclic PAS of the present invention, the pressure at which the reaction mixture is heated is not particularly limited, but is preferably a pressure that can exceed the reflux temperature of the reaction mixture under normal pressure. The pressure at which the reaction mixture is heated cannot be uniquely defined because it varies depending on the raw materials constituting the reaction mixture and its composition, the reaction temperature, etc. Preferably it can be 0.3 MPa or more, more preferably 0.4 MPa or more. Moreover, as a preferable upper limit of pressure, 10 MPa or less, More preferably, 5 MPa or less can be illustrated. In such a preferable pressure range, the time required for producing the cyclic PAS tends to be shortened. In the case where the amount of the organic polar solvent used in the production of the cyclic PAS is increased, that is, in the condition where the concentration of the linear PAS, the sulfidizing agent and the dihalogenated aromatic compound as raw materials in the reaction mixture is low, the preferable pressure range. There is a tendency that the effect of carrying out the reaction is particularly great, and the raw material consumption rate and / or the selectivity of the cyclic PAS as the target product can be further improved. The reason for this is not clear at present, but in the production of cyclic PAS, some of the raw materials such as dihalogenated aromatic compounds that are volatile under the heating conditions in the reaction exist in the gas phase in the reaction system, and the liquid phase The reaction with the reaction substrate may be difficult to proceed, and volatilization in the reaction system of such raw materials can be suppressed by setting the preferred pressure range so that the reaction proceeds more efficiently. I guess it will be. Further, in order to set the pressure at the time of heating the reaction mixture to the above preferable pressure range, the reaction mixture is reacted with an inert gas described later at an optional stage such as before starting the reaction or during the reaction, preferably before starting the reaction. It is also a preferable method to pressurize the system. Here, the gauge pressure is a relative pressure based on the atmospheric pressure, and is equivalent to a pressure value obtained by subtracting the atmospheric pressure from the absolute pressure.

In general, a cyclic compound is formed by forming a bond in a molecule of a linear compound having a relatively small number of repeating units as a precursor. Also in the cyclic PAS of the present invention, for example, it is considered that a cyclic PAS having a repeating unit number m is formed by an intramolecular reaction of a linear PAS having a repeating unit number m. In the present invention, the raw linear PAS is sulfided. It is presumed that by reacting with the agent, a linear compound having a relatively small number of repeating units that can be a precursor of the cyclic compound is generated, and the generation of the cyclic compound proceeds via this. Here, for example, when a linear PAS having a repeating unit number m and a linear PAS having a repeating unit number n react between molecules, a linear PAS having a repeating unit number (m + n) is generated. That is, in general, when producing a cyclic compound, not a few linear compounds due to intermolecular reactions are produced as a by-product, and it is important to preferentially proceed intramolecular reactions when producing cyclic compounds. In the case of PAS, it is generally known that linear PAS having a large number of repeating units tends to have poor solubility in an organic polar solvent, whereas the higher the temperature, the higher the solubility of the PAS component. Therefore, for the purpose of producing cyclic PAS, when it is desired to suppress the production of linear PAS, generally a low reaction temperature is adopted, and even in the production of known cyclic PAS, a reaction temperature exceeding the reflux temperature is not adopted. . On the other hand, in the case of producing a high molecular weight polymer of linear PAS, a high reaction temperature, which is a condition in which the PAS component is sufficiently dissolved in an organic polar solvent, is employed, and in the production of a known high molecular weight PAS. There is a strong tendency to employ a reaction temperature exceeding the reflux temperature, and it has been reported that PAS having a high molecular weight can be obtained in a high yield. In addition, the cyclic PAS can be obtained in a high yield in a short time in a high temperature range exceeding the reflux temperature of the reaction mixture, which is a temperature range in which a high molecular weight linear PAS can be easily obtained. In the temperature range preferably employed for the production of cyclic PAS, it is reported that not only cyclic PAS can be obtained in high yield, but also linear PAS produced as a by-product is easily obtained as a high molecular weight product. Has been. Here, the cyclic PAS and the linear PAS having a high molecular weight are, for example, greatly different in solubility in a solvent, so that the cyclic PAS and the linear PAS can be easily separated.

  In the production of the cyclic PAS of the present invention, various known polymerization methods and reaction methods such as a batch method and a continuous method can be employed. Further, the atmosphere in the production is preferably a non-oxidizing atmosphere, and it is preferably carried out in an inert gas atmosphere such as nitrogen, helium, and argon. In particular, from the viewpoint of economy and ease of handling, the nitrogen atmosphere is preferable. preferable. The reaction pressure is not particularly limited because it cannot be defined unconditionally depending on the type and amount of the raw material and solvent used, or the reaction temperature.

(Recovery process of cyclic polyarylene sulfide)
In the production of the cyclic PAS of the present invention, the cyclic PAS can be separated and recovered from the reaction mixture obtained by the above reaction. The reaction mixture obtained by the reaction contains cyclic PAS, linear PAS, and organic polar solvent, and other components include unreacted sulfidizing agent, dihalogenated aromatic compound, water, by-product salt, etc. There is also.

  In this reaction mixture, cyclic PAS tends to be dissolved in an organic polar solvent in a wide temperature range. On the other hand, linear PAS differs greatly in dissolution behavior from cyclic PAS. Specifically, most of the linear PAS tends to exist as a solid in the reaction mixture in a temperature range of 200 ° C. or lower.

  Therefore, by using such a difference in dissolution behavior in the reaction mixture of cyclic PAS and linear PAS, it is possible to separate cyclic PAS and linear PAS by simple solid-liquid separation. More specifically, the upper limit of the temperature range in which cyclic PAS and linear PAS can be separated by solid-liquid separation is 200 ° C. or lower, more preferably 150 ° C. or lower, and still more preferably 120 ° C. or lower. On the other hand, as a minimum temperature, 10 degreeC or more can be illustrated, 20 degreeC or more is preferable, 50 degreeC or more is more preferable, and 80 degreeC or more is still more preferable. Below this preferred upper temperature limit, the linear PAS contained in the reaction mixture tends to exist as a solid content, and the above-mentioned preferred weight average molecular weight PAS tends to become a solid content under these conditions. On the other hand, in this preferred temperature range, cyclic PAS in the reaction mixture has a strong tendency to be soluble in an organic polar solvent, and in particular, cyclic PAS in the preferred range in which the number of repeating units m of cyclic PAS is as described above is Strong tendency to dissolve in organic polar solvents. Above the exemplified lower limit temperature, the viscosity of the reaction mixture tends to be low, the solid-liquid separation operation is easy, and the separation between the solid component and the solution component tends to be excellent.

  In the above-described solid-liquid separation of the reaction mixture, it is possible to obtain linear PAS as a solid content, but it is difficult to completely separate the solid content and the liquid content as in the case of general solid-liquid separation. The solid content is separated as a liquid component such as an organic polar solvent in the reaction mixture. Therefore, if desired, a wet linear PAS in which the organic polar solvent derived from the reaction mixture is reduced by solvent replacement with a fresh solvent (not necessarily the organic polar solvent used in the reaction) is used. It is also possible to obtain a linear PAS in a dry state by additionally performing an operation of removing the liquid component contained. In the present invention, the linear polyarylene sulfide re-slurry step, which will be described later, allows the linear polyarylene sulfide to have fluidity and is sent to a reactor to be reused as a raw material.

(Reslurry process of linear polyarylene sulfide)
The linear polyarylene sulfide obtained as a solid content by the solid-liquid separation can be reused as a raw material. In order to continuously reuse the linear polyarylene sulfide that is a solid material as a raw material, it is desirable to have fluidity. Although there is no restriction | limiting in particular in the method for giving fluidity, Considering reusing as a raw material, it is desirable to perform reslurry by adding the same organic polar solvent as the organic polar solvent used as a raw material. As a specific method of reslurry, 1 to 50 times, more preferably 2 to 30 times, and even more preferably 4 to 15 times the amount of an organic polar solvent is added to linear polyarylene sulfide, and stirring is performed. The method of performing can be illustrated. In addition, when reslurry is performed, it is desirable to sufficiently stir so that the concentration of the linear polyarylene sulfide is uniform.
The mixed slurry containing the linear polyarylene sulfide and the organic polar solvent obtained by the reslurry is used as a raw material after a linear polyarylene sulfide reusing step described later.

(Recycling process of linear polyarylene sulfide)
In order to reuse the linear polyarylene sulfide as a raw material, it is desirable to send the mixed slurry obtained by the reslurry process to the reactor. Examples of the method for adjusting the amount of ionic components and the amount of arylene units in the reaction mixture based on the concentration of linear polyarylene sulfide measured by the method described later can be exemplified by the following two methods. . One is a method for adjusting the amount of the dihalogenated aromatic compound of the sulfiding agent added to the reactor, and the other is a method for adjusting the amount of the mixed slurry added to the reactor. Fewer adjustment items are advantageous in that the raw materials can be adjusted more precisely and the reactor can be simplified, and a method of adjusting the amount of mixed slurry added to the reactor is more advantageous. desirable. Further, the amount of the mixed slurry added to the reactor can be adjusted by adjusting the flow rate of the mixed slurry in the process of feeding the mixed slurry to the reactor.

  There is no particular limitation on the method of feeding the mixed slurry to the reactor. As a method of feeding liquid, a method of feeding using a pump, a method of feeding by gravity using a height difference, a method of feeding using a pressure difference, and the like can be considered. Further, when adjusting the flow rate of the mixed slurry, it is conceivable to use a control valve or the like. Among these liquid feeding and flow rate adjustment methods, the method of liquid feeding and flow rate adjustment using a pump and a control valve is desirable in that a stable flow rate can be obtained continuously.

  As described above, when adjusting the raw materials, the amount of the arylene unit per certain amount of the sulfur component contained in the reaction mixture is important. When the linear polyarylene sulfide is reused as a raw material, since the sulfur component and the arylene unit are also contained in the linear polyarylene sulfide, the concentration of the linear polyarylene sulfide is measured, and the reaction mixture contains It is necessary to adjust the amount of sulfur component and the amount of arylene units.

  There is no particular limitation on the method for measuring the concentration of linear polyarylene sulfide. Regarding the method for measuring the concentration of linear polyarylene sulfide, since linear polyarylene sulfide exists as a solid in the organic polar solvent, the organic polar solvent is removed from the mixed slurry by heating using an evaporator. A method of calculating from the weight ratio of the mixed slurry before the removal of the organic polar solvent and the solid content of the linear polyarylene sulfide after isolating the solid content of the arylene sulfide, and measuring the density of the mixed slurry and measuring the mixed slurry And a method of calculating using the density value of the polymer and the density value of the linear polyarylene sulfide and the organic polar solvent (hereinafter, density measuring method) can be considered. Since it is not necessary to remove the organic polar solvent, the measurement time can be shortened, and when the concentration of the linear polyarylene sulfide fluctuates, the flow rate of the mixed slurry is quickly adjusted to reduce the sulfur contained in the reaction mixture. It is desirable to use a density measurement method that allows the amount of arylene units contained in the reaction mixture per fixed amount of components to be adjusted more precisely within the preferred range and can improve the yield of cyclic polyarylene sulfide. .

  Since the density varies depending on the temperature, in the density measurement method, measuring the temperature in addition to the density of the mixed slurry determines the amount of arylene units contained in the reaction mixture per certain amount of the sulfur component contained in the reaction mixture. This is desirable because it can be adjusted more precisely within the preferred range and the yield of the cyclic polyarylene sulfide can be improved.

  There is no particular limitation on the method of measuring temperature and density. A method using a thermometer and a density meter, a method using a Coriolis mass flow meter, and the like are conceivable. Also, considering that it is desirable to measure the flow rate in order to adjust the flow rate of the mixed slurry according to the concentration of the linear polyarylene sulfide, the temperature, density and flow rate of the mixed slurry can be measured simultaneously. A method using a Coriolis mass flow meter is desirable.

  The measurement of the concentration of linear polyarylene sulfide should always be performed as the mixed slurry is fed to the reactor. The flow rate of the mixed slurry can be quickly adjusted according to the variation in the concentration of linear polyarylene sulfide in the mixed slurry. The amount of arylene units contained in the reaction mixture per certain amount of sulfur component contained in the reaction mixture can be adjusted more precisely within the preferred range, and the yield of cyclic polyarylene sulfide can be improved. This is desirable because it can be done.

  The present invention will be described more specifically with reference to the following examples. These examples are illustrative and not limiting.

<Measurement of cyclic polyphenylene sulfide production rate>
The production rate of the cyclic polyphenylene sulfide compound was subjected to qualitative quantitative analysis using HPLC. The measurement conditions for HPLC are shown below.
Apparatus: Shimadzu Corporation LC-10Avp Series Column: Mightysil RP-18 GP150-4.6 (5 μm)
Detector: Photodiode array detector (UV = 270 nm)

  The peaks detected in the HPLC analysis were classified into peaks derived from cyclic polyphenylene sulfide and peaks derived from the others. The ratio (area ratio) of the integrated value of the detected area of the peak derived from the cyclic polyphenylene sulfide to the integrated value of the detected area of all the detected peaks was defined as the cyclic polyphenylene sulfide purity.

<Measurement of linear polyarylene sulfide concentration>
The temperature and density of the mixed slurry of the organic polar solvent and the linear polyarylene sulfide were measured, and the concentration of the linear polyarylene sulfide was calculated by the following method. N-methylpyrrolidone (hereinafter sometimes abbreviated as NMP) was used as the organic polar solvent. The following calculation formula is calculated and formulated assuming that the density of linear polyarylene sulfide does not depend on temperature, and only the density of NMP has temperature dependence.
Measuring apparatus: Coriolis mass flow meter Micromotion 2700 series calculation formula: linear polyarylene sulfide concentration (wt%) = (− 0.3684 × mixed slurry temperature (° C.) + 357.36) × mixed slurry density (g / mL) )-(-0.6519 × mixed slurry temperature (° C.) + 372.85)

[Example 1]
In a stainless steel reactor equipped with a stirrer, 89.9 kg (1.60 kmol) of sodium hydrosulfide, 64.7 kg (1.62 kmol) of aqueous sodium hydroxide, N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) ) 3259.3 kg (32.9 kmol), p-dichlorobenzene (hereinafter sometimes abbreviated as p-DCB) 219.3 kg (1.49 kmol), and sealed in a nitrogen atmosphere at 250 ° C. for 4 hours. To obtain a polyarylene sulfide mixture containing linear polyphenylene sulfide and cyclic polyphenylene sulfide. The obtained polyarylene sulfide mixture was cooled to 80 ° C., taken out as a slurry, and subjected to pressure filtration at 0.3 MPa using a 600 mesh wire net. Linear polyphenylene sulfide was recovered as the solid content of the filter-on by pressure filtration, and cyclic polyphenylene sulfide was recovered as the filtrate.

  Reslurry was performed by adding 1200 kg of NMP to the recovered linear polyphenylene sulfide and stirring to obtain a mixed slurry containing linear polyphenylene sulfide and NMP. Next, in a stainless steel reactor equipped with a stirrer, sodium hydrosulfide 15.1 kg (0.27 kmol), sodium hydroxide 13.5 kg (0.34 kmol), NMP2345.0 kg (23.7 kmol), p-DCB 49.57 kg. (0.34 kmol) was charged, and the mixed slurry was subsequently fed to a stainless steel reactor equipped with a stirrer using a pump. At that time, the temperature, density, and flow rate of the mixed slurry to be continuously fed with a Coriolis mass flow meter installed in the pipe for feeding the mixed slurry are measured, and the reaction mixture in the stainless steel reactor with a stirrer is measured. The flow rate of the mixed slurry to be fed was adjusted so that the number of arylene units per 1 mol of sulfur component was 1.10 mol. After feeding the mixed slurry, stirring was performed to prepare a uniform raw material. Then, it was made to react at 250 degreeC in the state sealed in nitrogen atmosphere for 4 hours, and the polyarylene sulfide mixture containing linear polyphenylene sulfide and cyclic polyphenylene sulfide was obtained. The obtained polyarylene sulfide mixture was cooled to 80 ° C., taken out as a slurry, and subjected to pressure filtration at 0.3 MPa using a 600 mesh wire net. Linear polyphenylene sulfide was recovered as the solid content of the filter-on by pressure filtration, and cyclic polyphenylene sulfide was recovered as the filtrate. The purity of the recovered cyclic polyphenylene sulfide was 95%, and the yield of the cyclic polyphenylene sulfide when assuming that all sulfur components present in the reaction system were added to the PPS component was 18.4%.

[Example 2]
The mixed slurry containing linear polyphenylene sulfide and NMP obtained by the above method was mixed with sodium hydrosulfide 15.1 kg (0.27 kmol), sodium hydroxide 13.5 kg (0.34 kmol), NMP 2568.2 kg (25.9 kmol). ), When feeding to a stainless steel reactor with a stirrer containing 49.57 kg (0.34 kmol) of p-DCB, continuous concentration measurement is not performed, and NMP is heated with an evaporator from a partially extracted mixed slurry. As a result of calculating the concentration of linear polyphenylene sulfide by removing and measuring the weight of the solid content, it was 14.3 wt%. Therefore, assuming that the concentration of the linear polyphenylene sulfide is constant, the solution is fed so that the number of arylene units per 1 mol of sulfur component in the reaction mixture in the stainless steel reactor equipped with a stirrer is 1.10 mol. The flow rate of the mixed slurry was adjusted. After feeding the mixed slurry, stirring was performed to prepare a uniform raw material. The reaction was carried out at 250 ° C. for 4 hours in a sealed state under a nitrogen atmosphere to obtain a polyarylene sulfide mixture containing linear polyphenylene sulfide and cyclic polyphenylene sulfide. The obtained polyarylene sulfide mixture was cooled to 80 ° C., taken out as a slurry, and subjected to pressure filtration at 0.3 MPa using a 600 mesh wire net. Linear polyphenylene sulfide was recovered as the solid content of the filter-on by pressure filtration, and cyclic polyphenylene sulfide was recovered as the filtrate. The purity of the recovered cyclic polyphenylene sulfide was 89%, and the yield of the cyclic polyphenylene sulfide when assuming that all sulfur components present in the reaction system were added to the PPS component was 15.9%.

[Comparative Example 1]
The mixed slurry containing linear polyphenylene sulfide and NMP obtained by the above method was mixed with sodium hydrosulfide 15.1 kg (0.27 kmol), sodium hydroxide 13.5 kg (0.34 kmol), NMP 2568.2 kg (25.9 kmol). ), When feeding to a stainless steel reactor equipped with a stirrer containing 49.57 kg (0.34 kmol) of p-DCB, 818.6 kg of the mixed slurry was fed without measuring the concentration. After feeding the mixed slurry, a uniform reaction mixture was obtained by stirring. The reaction was carried out at 250 ° C. for 4 hours in a sealed state under a nitrogen atmosphere to obtain a polyarylene sulfide mixture containing linear polyphenylene sulfide and cyclic polyphenylene sulfide. The obtained polyarylene sulfide mixture was cooled to 80 ° C., taken out as a slurry, and subjected to pressure filtration at 0.3 MPa using a 600 mesh wire net. Linear polyphenylene sulfide was recovered as the solid content of the filter-on by pressure filtration, and cyclic polyphenylene sulfide was recovered as the filtrate. The purity of the recovered cyclic polyphenylene sulfide was 82%, and the yield of the cyclic polyphenylene sulfide when assuming that all sulfur components present in the reaction system were added to the PPS component was 14.0%.

Claims (2)

A method for producing a cyclic polyarylene sulfide by heating and reacting a reaction mixture containing at least a linear polyarylene sulfide, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent, the method comprising at least sulfidation From a polyarylene sulfide mixture containing a cyclic polyarylene sulfide and a linear polyarylene sulfide obtained by heating and reacting a reaction mixture containing an agent, a dihalogenated aromatic compound, and an organic polar solvent. In a method of reusing a mixed slurry containing a linear polyarylene sulfide obtained by separating sulfide and an organic polar solvent, the temperature, density and flow rate of the mixed slurry are measured, and the mixed slurry is included in the mixed slurry. Linear polyarylene sulf Measuring the concentration of de constantly adjust the flow rate of the mixed slurry according to the concentration of the linear polyarylene sulfide in the mixed slurry, the mixed slurry, sulfidizing agent, dihalogenated aromatic compound, an organic polar solvent A process for producing a cyclic polyarylene sulfide, which is recycled by feeding to a reaction mixture containing The method for producing a cyclic polyarylene sulfide according to claim 1, wherein the temperature, density and flow rate of the mixed slurry are measured by a Coriolis mass flow meter.

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